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HSQLDB example source code file (Like.java)

This example HSQLDB source code file (Like.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - HSQLDB tags/keywords

boolean, character, like, percent_char, percent_char, string, string, stringbuffer, stringbuffer, underscore_char, underscore_char

The HSQLDB Like.java source code

/*
 * For work developed by the HSQL Development Group:
 *
 * Copyright (c) 2001-2010, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 *
 * For work originally developed by the Hypersonic SQL Group:
 *
 * Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the Hypersonic SQL Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE HYPERSONIC SQL GROUP,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * on behalf of the Hypersonic SQL Group.
 */


package org.hsqldb;

import org.hsqldb.lib.StringUtil;

/**
 * Reusable object for processing LIKE queries.
 *
 * Enhanced in successive versions of HSQLDB.
 *
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @version 1.8.0
 * @since Hypersonic SQL
 */

// boucherb@users 20030930 - patch 1.7.2 - optimize into joins if possible
// fredt@users 20031006 - patch 1.7.2 - reuse Like objects for all rows
class Like {

    private char[]   cLike;
    private int[]    wildCardType;
    private int      iLen;
    private boolean  isIgnoreCase;
    private int      iFirstWildCard;
    private boolean  isNull;
    Character        escapeChar;
    boolean          hasCollation;
    boolean          optimised;
    static final int UNDERSCORE_CHAR = 1;
    static final int PERCENT_CHAR    = 2;

    Like(Character escape, boolean collation) {
        escapeChar   = escape;
        hasCollation = collation;
    }

    /**
     * param setter
     *
     * @param s
     * @param ignorecase
     */
    void setParams(Session session, String s, boolean ignorecase) {

        isIgnoreCase = ignorecase;

        normalize(session, s);

        optimised = true;
    }

    /**
     * Resets the search pattern;
     */
    void resetPattern(Session session, String s) {
        normalize(session, s);
    }

    private String getStartsWith() {

        if (iLen == 0) {
            return "";
        }

        StringBuffer s = new StringBuffer();
        int          i = 0;

        for (; (i < iLen) && (wildCardType[i] == 0); i++) {
            s.append(cLike[i]);
        }

        if (i == 0) {
            return null;
        }

        return s.toString();
    }

    /**
     * Method declaration
     *
     *
     * @param o
     *
     * @return
     */
    Boolean compare(Session session, String s) {

        if (s == null) {
            return null;
        }

        if (isIgnoreCase) {
            s = session.database.collation.toUpperCase(s);
        }

        return compareAt(s, 0, 0, s.length()) ? Boolean.TRUE
                                              : Boolean.FALSE;
    }

    /**
     * Method declaration
     *
     *
     * @param s
     * @param i
     * @param j
     * @param jLen
     *
     * @return
     */
    private boolean compareAt(String s, int i, int j, int jLen) {

        for (; i < iLen; i++) {
            switch (wildCardType[i]) {

                case 0 :                  // general character
                    if ((j >= jLen) || (cLike[i] != s.charAt(j++))) {
                        return false;
                    }
                    break;

                case UNDERSCORE_CHAR :    // underscore: do not test this character
                    if (j++ >= jLen) {
                        return false;
                    }
                    break;

                case PERCENT_CHAR :       // percent: none or any character(s)
                    if (++i >= iLen) {
                        return true;
                    }

                    while (j < jLen) {
                        if ((cLike[i] == s.charAt(j))
                                && compareAt(s, i, j, jLen)) {
                            return true;
                        }

                        j++;
                    }

                    return false;
            }
        }

        if (j != jLen) {
            return false;
        }

        return true;
    }

    /**
     * Method declaration
     *
     *
     * @param pattern
     * @param b
     */
    private void normalize(Session session, String pattern) {

        isNull = pattern == null;

        if (!isNull && isIgnoreCase) {
            pattern = session.database.collation.toUpperCase(pattern);
        }

        iLen           = 0;
        iFirstWildCard = -1;

        int l = pattern == null ? 0
                                : pattern.length();

        cLike        = new char[l];
        wildCardType = new int[l];

        boolean bEscaping = false,
                bPercent  = false;

        for (int i = 0; i < l; i++) {
            char c = pattern.charAt(i);

            if (bEscaping == false) {
                if (escapeChar != null && escapeChar.charValue() == c) {
                    bEscaping = true;

                    continue;
                } else if (c == '_') {
                    wildCardType[iLen] = UNDERSCORE_CHAR;

                    if (iFirstWildCard == -1) {
                        iFirstWildCard = iLen;
                    }
                } else if (c == '%') {
                    if (bPercent) {
                        continue;
                    }

                    bPercent           = true;
                    wildCardType[iLen] = PERCENT_CHAR;

                    if (iFirstWildCard == -1) {
                        iFirstWildCard = iLen;
                    }
                } else {
                    bPercent = false;
                }
            } else {
                bPercent  = false;
                bEscaping = false;
            }

            cLike[iLen++] = c;
        }

        for (int i = 0; i < iLen - 1; i++) {
            if ((wildCardType[i] == PERCENT_CHAR)
                    && (wildCardType[i + 1] == UNDERSCORE_CHAR)) {
                wildCardType[i]     = UNDERSCORE_CHAR;
                wildCardType[i + 1] = PERCENT_CHAR;
            }
        }
    }

    boolean hasWildcards() {
        return iFirstWildCard != -1;
    }

    boolean isEquivalentToFalsePredicate() {
        return isNull;
    }

    boolean isEquivalentToEqualsPredicate() {
        return iFirstWildCard == -1;
    }

    boolean isEquivalentToNotNullPredicate() {

        if (isNull ||!hasWildcards()) {
            return false;
        }

        for (int i = 0; i < wildCardType.length; i++) {
            if (wildCardType[i] != PERCENT_CHAR) {
                return false;
            }
        }

        return true;
    }

    boolean isEquivalentToBetweenPredicate() {

        return iFirstWildCard > 0
               && iFirstWildCard == wildCardType.length - 1
               && cLike[iFirstWildCard] == '%';
    }

    boolean isEquivalentToBetweenPredicateAugmentedWithLike() {
        return iFirstWildCard > 0 && cLike[iFirstWildCard] == '%';
    }

    String getRangeLow() {
        return getStartsWith();
    }

    String getRangeHigh() {

        String s = getStartsWith();

        return s == null ? null
                         : s.concat("\uffff");
    }

    public String describe(Session session) {

        StringBuffer sb = new StringBuffer();

        sb.append(super.toString()).append("[\n");
        sb.append("escapeChar=").append(escapeChar).append('\n');
        sb.append("isNull=").append(isNull).append('\n');
        sb.append("optimised=").append(optimised).append('\n');
        sb.append("isIgnoreCase=").append(isIgnoreCase).append('\n');
        sb.append("iLen=").append(iLen).append('\n');
        sb.append("iFirstWildCard=").append(iFirstWildCard).append('\n');
        sb.append("cLike=");
        sb.append(StringUtil.arrayToString(cLike));
        sb.append('\n');
        sb.append("wildCardType=");
        sb.append(StringUtil.arrayToString(wildCardType));
        sb.append(']');

        return sb.toString();
    }
}

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